Current busbar

ABSTRACT

Current busbar for anode or cathode for use in production of aluminium from alumina in an electrolysis bath in an electrolysis cell, comprising ends or sections that during operation shall be within the electrode body are formed as horizontally oriented conical bodies and cylindrical or conical grooves with largest horizontal cross section dimension within said grooves, such that by sliding in correspondingly formed cooper rails on the external parts of the busbar, said bodies and rails are releasable joined.

FIELD OF THE INVENTION

The present invention relates to current bus bars for anodes or cathodes for use in production of aluminium by electrolysis of alumina in an electrolysis bath in an electrolysis cell.

BACKGROUND OF THE INVENTION

Production of primary aluminium takes place by electrolysis of alumina solved in a melted halogenide electrolysis bath, for example an electrolysis bath comprising cryolite. By electrolysis, compositions that are split into ions in the electrolyte are reduced at the cathode and oxidized at the anode, by use of impressed current. Thereby aluminium can be produced at the cathode and oxygen at the anode. The process used for production of aluminium, the Hall-Heroult-process, was developed almost simultaneously and independent by the American Hall and the Frenchman Heroult for more than one hundred years ago. For both the anode and the cathode it is most common to use an electrode body of carbon, with one or more current busbars embedded within the carbon. The function of the current busbars are to deliver current to or from the electrode body, to conduct heat away from the electrolysis bath, and to contribute to the mechanical strength and connection. The current busbars are connected directly or via further means to an outer current circuit.

In patent publication WO 02/42525 various embodiments of current busbars for anodes and cathodes are illustrated, with associated description of essential features for current busbars.

Despite many years of development a demand still exists for improvement of the electrolysis cell, including the current busbars. Particularly a demand exists for current busbars having large heat conduction away from the electrolysis bath. Further, it would be preferable with current busbars with reduced voltage drop, which inter alia is related to the contact area towards the carbon. Further, it would be beneficial with current busbars that, with regard to the anodes, do not require casting to the carbon via a cast iron lining or -socket formed by liquid cast iron being poured into the gap between adapted holes in the electrode body and inserted anode nipples, which is made possible by the holes in the electrode body having slightly larger diameter than the nipples. Accordingly, a demand exists for avoiding the use of a cast iron lining for fastening the current busbars to the carbon, whereby the current busbars can be improved with respect to mounting and demounting to the carbon. A demand also exists for joining embedded parts or sections of current busbars to the further parts of the current busbars, in a simple and releasable way, with good electrical, thermal and mechanical contact.

SUMMARY OF THE INVENTION

With the present invention the above-mentioned demands are met, by providing a novel type of current busbar for anode or cathode for use in production of aluminium from alumina in an electrolysis bath in an electrolysis cell, which current busbar comprises one or more ends or sections that during operation shall extend out of an electrode body, and one or more ends or sections that during operation shall be embedded or within the electrode body. The current busbar is distinguished by comprising both or one of the features as follows:

ends or sections that during operation shall be within the electrode body are formed as one or more in substance horizontally oriented conical bodies with largest horizontal cross section diameter within the electrode body, such that by sliding said bodies axially into one or more adapted conical holes in the electrode body said bodies will be embedded and kept into the electrode body, and

said conical bodies or elements connected thereto are manufactured from steel or steel over a copper core, and are provided with one or more in substance horizontally formed cylindrical or conical grooves with largest horizontal cross section dimension within said grooves, such that by sliding in correspondingly formed copper rails on the external parts of the busbar, said bodies and rails are releasably joined.

With in substance horizontally oriented means in substance parallel with the electrolysis bath or horizontal with few degrees deviation, most preferable completely horizontal.

With conical body it is meant an elongated body having increasing or decreasing cross section dimensions over a substantial part of its length, preferably the full length. The corresponding is true for conical holes. With a cylindrical groove or body it is meant an even cross section over a substantial part of the length, preferably all the length except from optional tapering or grounding off at the ends. Cylindrical does not necessarily mean round cross section, the only requirement is that the cross section is the same along the length. The cross section therefore can be triangular, four-sided, five-sided, round, elliptical, T-formed or take any other form, which also is true for conical bodies, provided that the further distinguishing features are maintained. It is also important to be aware of that the cylindrical body can extend in vertical direction, such that a part of the cylinder body, along the full or parts of its length, can extend out for example from the electrode body.

The feature of the largest horizontal cross section dimension of the conical body and cylindrical body to be within respectively the electrode body and the groove when these are joined, hinder that bodies as joined can be separated from each other by pulling in vertical direction, orthogonal to the longitudinal axis of the conical body and cylindrical body. For joining into the electrode body it is not required with cast iron lining, ramming paste, ramming mass or glue, which provides savings both with respect to materials and labour. The conical form ensures good thermal, electrical and mechanical contact even after beginning of wearing out the conical bodies. A copper rail within a steel groove will during operation have very good electrical thermal and mechanical contact because the copper has larger thermal expansion than the steel, such that an appropriate tolerance for joining at room temperature, for example 0.15-0.5 mm clearance, will be filled out by expansion of the copper. Thereby a releasable joining is achieved with good electrical, thermal and mechanical contact, which provides savings with respect to labour and possibility for easy replacement of parts of a current busbar.

It is preferable if the cross section of the parts that are to be built into the electrode body has form of a circle, triangle or quadrangle under or below a high and narrow rectangle, such that the largest horizontal dimension of the circle, triangle or quadrangle is at least four times larger than the horizontal dimension of the rectangle. This results in simple and solid fastening.

The current busbar according to the invention is preferably formed such that different materials in the longitudinal direction of the busbar are welded together by linear friction welding, surfacing friction welding, rotation friction welding, induction welding, laser welding or electron beam welding, because of good electrical, thermal and mechanical contact.

The current busbar according to the invention can preferably be manufactured with pure aluminium, aluminium alloy, copper or copper alloy used as construction material in the parts furthest away from the electrode body and in a distance close to or within the electrode body, with a protective lining of steel for parts within or close to the electrode body. Thereby the heat conduction is maximized while the electrical resistance is minimized and the electrolysis cell can be operated at high amperage.

The current busbar according to the invention is preferably either an anode hanger or a cathode steel. The current busbars according to the invention is preferably surface treated with wolfram, for increased life. The embodiment of the current busbar with only the distinguishing feature with the copper rails, can include traditional nipples as the ends or sections that during operation are within the electrode body.

With the present invention also an electrode body is provided, distinguished in that it in substance consists of carbon and has adapted grooves for mounting of the current busbars according to the present invention. The conical holes in the electrode body are preferably slightly longer than the conical bodies, such that said conical bodies will fit into said conical holes even after some wearing out.

With the present invention also an electrode is provided, distinguished in that it comprises current busbars according to the present invention joined with electrode body according to the present invention.

DRAWINGS

The invention is further illustrated by drawings, of which:

The FIGS. 1 a and 1 b illustrate an anode hanger according to the present invention.

FIG. 2 illustrates another embodiment of an anode hanger according to the present invention.

FIG. 3 illustrates a third embodiment of an anode hanger according to the present invention.

DETAILED DESCRIPTION

First, reference is made to the FIGS. 1A and 1B, which illustrate an anode hanger according to the present invention, viewed orthogonal to the conical body 1, for FIG. 1A, and along the longitudinal axis of the conical body, for FIG. 1B, respectively. The conical body is joined with an electrode body 2 by being slided into a conical groove 3 with form corresponding to the conical body. As apparent from the figure the largest horizontal cross section dimension for the conical body is within the electrode body, such that the conical body as joined with the electrode body during operation is fastened and kept in place into the electrode body. The conical body is on the upper side fastened into a narrower element, with cross section form as a rectangle with far smaller horizontal dimension than the conical body, such that even though the groove in the electrode body is upwardly open along all or parts of the length of the conical body, said conical body cannot escape from the electrode body during operation. In the illustrated embodiment an inner core of copper 4 is provided in the conical body, the rectangle and an above positioned connecting beam. Outside the copper is a steel lining 5. The upper part of the anode hanger is formed by an aluminium part 6, joined with the copper by friction welding. In the illustrated embodiment of the current busbar, in form of an anode hanger, copper and aluminium is used in a large extent, which is preferable with respect to thermal and electrical conductivity. The whole anode hanger could be prepared by steel, but out of consideration to thermal and electrical conductivity preferably copper and optionally aluminium are used extensively. For increased heat conduction cooling ribs can be provided in addition to using increased dimension for the different parts of the anode hanger.

Reference is further made to FIG. 2 that illustrates another embodiment of an anode hanger according to the invention, more specifically an anode hanger where a copper rail 7 is arranged to be slided into a correspondingly formed groove in a cylindrical steel body 8 that is to be embedded into the electrode body. The copper rail and the groove are formed with tolerances such that the copper rail relatively easy can be slided into the groove in the steel body at room temperature. By heating during operation in the cell copper will expand more than steel such that a good electrical, thermal and mechanical connection between the copper and the steel is achieved.

Reference is made to FIG. 3 where a further embodiment of an anode hanger according to the invention is illustrated, more specifically a steel nipple 9 with groove for sliding in of a copper rail 7 is illustrated. A number of steel nipples can be passed into the copper rail 7.

Regarding the anode hangers illustrated on FIGS. 2 and 3, the cylindrical steel body 8 and steel nipples 9 could be replaced with respect to a conical body of massive steel or with steel lining around a copper core, with grooves for fastening of the copper rail, with the groove either directly into the conical body or above, for example in a connecting beam. The most preferred embodiment of the invention (not illustrated) comprises both a conical body and fastening to the above part of the anode hanger by use of a copper rail, because said embodiment includes all the advantages of the invention.

EXAMPLE

An anode hanger with a conical section embedded into the electrode body illustrates some of the advantages of the invention. The cylinder section has length 1.5 m and consists of a 100 to 140 mm diameter bolt under a small, high rectangle where in total 100 mm vertical rectangle side is embedded into electrode body. The resulting contact area with the electrode body is about 726 500 mm². A standard anode hanger with 4 nipples has a contact area of typical 281 000 mm². The contact area has thereby increased 2.59 times. By having an adapted cross section area, choice of materials and form of the ends or sections of the current busbar that during operation shall extend out from the electrode body, very preferable properties can be achieved with respect to the demands that are met with the present invention 

1. Current busbar for anode or cathode for use in production of aluminium from alumina in an electrolysis bath in an electrolysis cell, which current busbar comprises one or more ends or sections that during operation shall extend out of an electrode body, and one or more ends or sections that during operation shall be within the electrode body, wherein ends or sections that during operation shall be within the electrode body are formed as one or more in substance horizontally oriented conical bodies with largest horizontal cross section diameter within the electrode body, such that by sliding said bodies axially into one or more adapted conical holes in the electrode body said bodies will be embedded and kept into the electrode body, and said conical bodies or elements connected thereto are manufactured from steel or steel over a copper core, and are provided with one or more in substance horizontally formed cylindrical or conical grooves with largest horizontal cross section dimension within said grooves, such that by sliding in correspondingly formed copper rails on the external parts of the busbar, said bodies and rails are releasably joined.
 2. Current busbar according to claim 1, wherein the cross section of the parts that are to be within the electrode body have form as a circle, triangle or quadrangle under or over a high and narrow rectangle, such that the largest horizontal dimension of the circle, triangle or quadrangle is at least four times larger than the horizontal dimension of the rectangle.
 3. Current busbar for anode or cathode for use in production of aluminium from alumina in an electrolysis bath in an electrolysis cell, which current busbar comprises one or more ends or sections that during operation shall extend out of an electrode body, and one or more ends or sections that during operation shall be within the electrode body, wherein ends or sections that during operation shall be within the electrode body are formed as one or more in substance horizontally oriented conical bodies with largest horizontal cross section diameter within the electrode body, such that by sliding said bodies axially into one or more adapted conical holes in the electrode body said bodies will be embedded and kept into the electrode body.
 4. Current busbar for anode or cathode for use in production of aluminium from alumina in an electrolysis bath in an electrolysis cell, which current busbar comprises one or more ends or sections that during operation shall extend out of an electrode body, and one or more ends or sections that during operation shall be within the electrode body, wherein the transfer between steel in parts of the current busbar that are to be within or close to the electrode body and copper in external parts from the electrode body are formed as one or more in substance horizontally formed cylindrical or conical grooves in the steel with largest horizontal cross section dimension within said grooves, and correspondingly formed copper rails on the external parts of the current busbar, such that by sliding in the copper rails into the steel grooves the parts will be releasably joined.
 5. Current busbar according to claim 1, wherein the current busbar is an anode hanger.
 6. Current busbar according to claim 1, wherein the current busbar is a cathode steel.
 7. Current busbars according to claim 1, wherein pure aluminium, aluminium alloy, copper or copper alloy is used as construction material in the parts furthest away from the electrode body and in a distance close to or within the electrode body, with a protective lining of steel for parts within or close to the electrode body.
 8. Electrode body, consisting of carbon and is provided with adapted grooves for mounting of current busbars according to claim
 1. 9. Electrode body according to claim 8, wherein the conical grooves in the electrode body is slightly longer than the conical bodies, such that said conical bodies will fit into said conical grooves even though they have been slightly worn-out.
 10. Electrode, comprising current busbars according to claim 1 joined with electrode body according to claim
 8. 